1. Technical Field
The disclosed embodiments relate generally to wireless communication systems, and more particularly, to power amplifiers and noise cancellation techniques used in radio front end circuitry for up-converting and down-converting transmission signals.
2. Background Information
Signals transmitted by a transceiver device may be received by a receive path of the transceiver device. Reception of transmit signals increases the receiver's noise floor and therefore reduces the receiver's sensitivity.
Conventional radio frequency (RF) front-ends utilize a single front-end filter for the transmit (Tx) path and a single front-end filter for the receive (Rx) path. The filter in the Tx path typically has strong rejection to remove out-of-band (Tx) noise that may leak into the Rx path. This Tx filter has relatively high insertion loss to support sharp rejection and the gain of the transmitter's power amplifier and its P1 dB are relatively high to compensate for the insertion loss of filter.
The Rx path also includes an Rx filter that has strong rejection to remove out-of-band Tx power and harmonics that may leak into the Rx path. The Rx filter has relatively high insertion loss to support sharp rejection thus increasing the Rx noise floor. The Rx path also includes a low noise amplifier (LNA) with relatively high gain to compensate the filter insertion loss and to achieve good noise figure. As a result, conventional solutions to address the problems of out-of-band Tx noise leaking into the Rx path utilize filters for both the Tx and Rx paths which result in a significant noise floor penalty in the Rx path and higher gain and power at the Tx path, resulting in increased power consumption, and high parts count.
Therefore, it is desirable to have noise canceler for use in a transceiver to reduce the amount of Tx noise leaking into the Rx path while overcoming the problems associated with conventional systems.